Multicomponent Cascade Reaction of HKAs: Synthesis of Highly Functionalized 5H-Chromeno[4,3-d]pyrimidines

A novel protocol was developed for the construction of highly functionalized 5H-Chromeno[4,3-d]pyrimidines (CMPDs) from 3-formylchromones, heterocyclic ketene aminals and amidine hydrochlorides via an unprecedented cascade reaction involving the interesting ring-opening...

Orthoamide und Iminiumsalze, CI. Umsetzungen von N,N,N′,N′-Tetramethylharnstoffdiethylacetal mit CH2-aciden Verbindungen

N,N,N′,N′-Tetramethylurea diethylacetal reacts with CH2-acidic compounds as benzylcyanide, cyanoacetic acid derivatives malonodinitrile and nitromethane to give ketene aminals or ketene-O,N-acetales. Low polar solvents favour mostly the formation of ketenaminals. The yields of ketenaminals and ketene-O,N-acetals can be improved in some cases by addition of trimethylsilyldimethylamine. The reactions of the urea acetal with diethylmalonate, ore acetyl acetone, stops at the stage of the N,N′,N″-permethylated guanidinium salts with carbanionic counterions. The formation of bis(dimethylamino)methylene-diethylmalonate from the urea acetal and diethylmalonate can be initiated by addition of trimethylsilyldimethylamine/trimethylsilylcyanide. N,N,N′,N′,N″,N″-Hexamethylguanidinium cyanide is formed in the analogous reactions of the urea acetal with N,N-dimethylcyanacetamide or diethylsuccinate. The N,N′,N″-Hexamethyl-guanidinium nitrite can be obtained from the urea acetal and nitropropane.

Orthoamide und Iminiumsalze, IIIC. Weitere Ergebnisse bei der Umsetzung von Orthoamiden der Alkincarbonsäuren mit CH2- und CH2/NH-aciden Verbindungen

The 1,1-bis(dimethylamino)-1,3-butadienes (keten aminals) 11a–l are prepared from orthoamide derivatives of alkyne carbonxylic acids 9b, d, e, i and CH2-acidic compounds 10a–c, f–h, k, o. The C-silylated orthoamide derivative 9c shows an ambivalent behaviour towards CH-acidic compounds. Reactions of 9c with strong CH2-acidic compounds like the nitro alkanes 10m, n and strongly enolized carbonyl compounds as methyl acetoacetate, cyanoacetamide, dibenzoylmethane, 1,3-dimethylbarbituric acid proceed under desilylation to give the ketene aminals 11u–z. In contrast to these reactions, the C-silylated ketene aminals 11o–t are obtained from 9c and weaker CH2-acidic compounds as dimethyl malonate, cyanoacetic acid derivatives and benzylcyanides. CH2/NH2-acidic compounds [cyanoacetamide (10d) and N-ethyl-cyanoacetamide (10f)] react with the orthoamide derivatives 9b, e–g at the acidic carbon-hydrogen bond to give the ketene aminals 11ac, ad, af, ag, ai, which cyclize to the pyridones 14a–d, d–g on heating. From the reaction of the orthoamide 9d with cyanoacetamide the pyridone 14c results directly. The persubstituted pyridone derivative 19 is formed by the reaction of cyanoacetamide with a mixture of the isomeric orthoamides 15 and 16. The 5,5-diamino-2,4-pentadienamide 11v attacks the orthoamide 9a at C3/C1. In the product 20 a cross conjugated multiple bond system is formed which contains an 1-aza-2,3-diamino function and a further ketene aminal function.